Tool for removing concentric knockouts

ABSTRACT

A tool for removing concentric ring knockouts from electrical conduit boxes of various construction after removal of the center disc knockout. The tool has opposed groove defining means set at an angle relative to each other and spaced apart by a distance less than a minimum predetermined diameter of a ring knockout to be removed, the groove defining means being adapted to alternately engage opposite points on the ring knockout in response to a backward and forward movement of the tool so as to fracture the knockout by a series of oscillatory movements about a pivot point until the points of connection of the ring knockout with the rest of the box fracture.

United States Patent [191 Pepe [54] TOOL FOR REMOVING CONCENTRIC KNOCKOUTS [76] Inventor: Frank W. Pepe, 637 Prospect Drive,

Lorship, Conn.

22 Filed: May 20,1971 21 Appl.No.: 145,387

[52] Cl ..29/267, 29/280, 81/3.46 R

51 Int. Cl. ..B23p 19 04 [58] FieldotSea'rch ..7/l7;29/267, 275,

[56] References Cited UNlTED STATES PATENTS 2,571,401 10/1946 Williams ..8l/3.46A 1,581,119 4/1926 Herring ..72/458 [111 3,736,6 3 1 51 June5, 1973 1,711,062 4/l929 Purinton ..7/17

Primary Examiner-Othell M. Simpson Assistant Examiner-Mark S. Bicks Attorney-Martin D. Wittstein [57] ABSTRACT A tool for removing concentric :ring knockouts from electrical conduit boxes of various construction after removal of the center disc knockout. The tool has opposed groove defining means set at an angle relative to each other and spaced apart by a distance less than a minimum predetermined diameter of a ring knockout to be removed, the groove defining means being adapted to alternately engage opposite points on the ring knockout in response to a backward and forward movement of the tool so as to fracture the knockout by a series of oscillatory movements about a pivot point until the points of connection of the ring knockout with the rest of the box fracture.

7 Claims, 5 Drawing Figures PAIENTEDJUH 5 I975 3.733343 INVENTOR. FRANK W. PEPE 1M 12 (um ATTORNEY 1 TOOL FOR REMOVING CONCENTRIC KNOCKOUTS BACKGROUND OF THE INVENTION This invention relates to a novel electricians hand tool and more particularly to a tool for removing concentric r'ing knockouts from electrical conduit boxes and the like.

This invention is an improvement on the ring knock out tool disclosed and claimed in my copending patent application Ser. No. 706,899, filed Feb. 20, 1968, now U.S. Pat. No. 3,579,797, issued May 25, 1971.

In the construction industry it is well known that sub stantially all wiring of buildings, both commercial and residential, is initiated, coupled and/or terminated in metal boxlike enclosures such as fuse boxes, junction boxes, terminal outlet or switch boxes, and the like, all of which take a large variety of shapes and sizes depending on the location and function of the boxes. In standard practice, according to most electrical wiring codes, all electric wires must be connected either to utility or control components, or to each other, within these boxes which are customarily secured to a suitable surface and provided with some type of cover member so that wire connections or ends are not readily accessible.

, In order to provide access to the interior of the boxes for the wires entering or leaving a particular box, as the case may be, the boxes are provided with a number of apertures, usually on all sides thereof except on the cover member. These apertures are initially closed by frangible or removable knockout members which maintain the sides of the box closed until it is desired to insert a wire therethrough. These members take a variety of forms and shapes; however, most must be broken, fractured or otherwise mutilated in order to remove them.

In order to eliminate any tension or pull on the terminal connections of wire within the box, the wires are secured to the side of the box where they pass through an aperture. This is usually accomplished by providing a socket which is secured within the aperture in the side of the box, the socket itself having screws or other suitable means for tightly gripping the outer covering or sheathof the wires.

Since electric wire is manufactured in different ways, e.g., plastic insulated, flexible helically wound meta] sheathed (known in the trade as BX cable) and rigid pipe or conduit enclosed, it is necessary to have holding sockets of varying diameter to accommodate the particular type of wire being used. It is therefore necessary to have apertures with correspondingly varying diameters to accommodate the sockets.

In order to avoid duplication of boxes simply to pro vide apertures of the proper diameter, it has become customary to manufacture such boxes with large apertures having a type of closure member therefore which will provide one of two aperture sizes depending on the manner of removal of the aperture closure member. Such a member is generally known as the concentric knockout and generally comprises a circular disc defined by a score or weakened line on the side of the box extending over almost a complete circle, but discontinued over a short arc to provide a small non-weakened connecting portion for the disc to rest of the box side. A concentric ring knockout is defined by a concentric score or weakened line which extends in two almost semi-circular but unjoined arcs around the disc, adjacent ends of each concentric are being connected to the inner circle where the latter terminates at the nonweakened connecting portion. Thus the ring knockout does not interfere with a connecting bridge now defined between the box side and the disc and is itself connected to the box side at a non-weakenecl point diametrically opposed from the disc connecting bridge. By selectively removing either the disc alone or the disc and concentric ring it is possible to obtain an aperture having either of two predetermined diameters which, by appropriate selection of sizes, will accommodate most commercial wire sizes.

These knockouts are customarily removed by a complicated procedure which requires placing a screwdriver or similar blunt instrument on the disc knockout and striking it with a hammer until the disc is sufficiently fractured from the box side and from the ring knockout to permit the disc to be manually bent back and forth until it is completely fractured. The tip of the screwdriver is then placed under the ring knockout at a point 90 from the point of non-weakened connection between the ring and the box side and, by using the opposite side of the ring knockout as a fulcrum, the screwdriver is forced downwardly so that the first mentioned side of the ring is broken from the box side and bent upwardly as much as ,possiblleThis procedure is repeated with the screwdriver tip under the opposite side of the ring, using the opposite side of the aperture as a fulcrum. A pliers is now used to press the two up wardly bent halves ofthe ring knockout together and to bend them back and forth until the points of nonweakened connection is broken to permit complete removal of the ring. This procedure is awkward, time consuming and requires the use of several tools.

In the above mentioned application, there is dis; closed and claimed a tool for removing concentric ring knockouts in a highly simple and efficient manner and which obviates or eliminates many of the disadvantages of the foregoing knockout removal procedure. Although the tool disclosed in the prior application works quite satisfactorily for the intended purpose, it has not yet enjoyed extensive commercial. success in view of the fact that itjs composed of particularly shaped parts which require special maching procedures to form, and

also relatively movable parts which require not only special maching procedures but also assembly operations, all of which involve a certain degree of manufacturing cost. As a result, the ultimate selling price of the tool is out of proportion with the estimated value of the tool to the electrician who thereupon continues to use the old multiple tool procedure for removing the knockout in preference to purchasing a knockout tool.

In addition, by virtue of the fact that the prior tool has opposed gripping means which simultaneously engage opposite portions of the ring knockout in order to effect the oscillatory fracturing movement of the ring knockout, the tool was particularly designed for use with a predetermined size of ring knockout and therefore was not practically or efficiently suitable for use with ring knockouts of other than the predetermined size.

SUMMARY OF THE INVENTION knockout operation that the tool be of any particularly design which requires special shaping of parts other than those which can be performed by a simple punching operation and further that it is not necessary that both opposite portions be simultaneously gripped during the fracturing operation, thereby eliminating the necessity for relatively movable parts as required in the prior tool and facilitating the use of a single tool for removing knockouts of several different sizes. It has been discovered that a tool having stationary oppositely disposed gripping means can be utilized to remove ring knockouts of several different sizes by continuing a backward and forward motion of the tool with the oscillatory movement of the prior tool in a manner fully described hereinbelow.

The improvements of the present invention are embodied generally in a tool having an elongate body member with a handle portion at a rearward end thereof and a one piece, unitary sheet member gripping structure integrally formed with the body member and located at the other or forward end thereof. The gripping structure comprises generally opposed gripping means in the form of a pair of oppositely facing grooves formed in the body member adjacent the forward end thereof, the grooves being oriented generally so as to open toward the forward and rearward ends of the body member. The grooves are spaced apart by a distance slightly less than the interval diameter of the smallest ring knockout for which the tool is designed so that it can readily be inserted into the aperture of the knockout, and moved forwardly and rearwardly to al ternately engage opposite portions of a ring knockout with the opposed gripping means. The forwardly facing groove is spaced from the forward end of the body member a distance sufficient toprovide an elongate bearing surface forwardly of the groove, and there is a second elongate bearing surface disposed just rearwardly of the rearwardly facing groove. The bearing surfaces and the grooves are disposed at an angle relative to each other.

By this construction, it is possible to insert the tool into the aperture of ring knockouts of a number of different diameters and successively or alternately engage opposite portions of the ring knockout with one or the other of the gripping grooves by shifting the tool backwards and forwards, and fracturing the ring knockout by importing a clockwise or counter-clockwise oscillatory movement to the tool with each successive backward or forward movement thereof. The diameter of the ring knockout which the present tool can handle is limited only by the extent of the bearing surfaces forwardly and rearwardly of the gripping grooves.

Another feature of the present invention, in addition to the removal of concentric ring knockouts from a conduit box, is the provision of means for easily removing the center disc knockout formed as described above. Thus the gripping structure is further provided with a blunt pointed nose portion adapted to be placed against the disc knockout to partially disengage the knockout from the wall of the conduit box by striking the other end of the tool with the users hand or any suitable instrument. A slot is provided in the gripping structure just rearwardly of the nose portion which is placed over the disc knockout so that the latter can be completely fractured from the box by a twisting action of the tool.

Having briefly described the general nature of the present invention, it is a principal object thereof to provide a novel hand tool for the removal of concentric ring knockouts from electrical conduit boxes.

It is another object of the present invention to provide a hand tool for removing concentric ring knockouts which avoids thedisadvantages of the tool disclosed in the above mentioned earlier filed application but yet retains the significant advantages.

It is a more specific object of the present invention to provide a hand tool for removing concentric ring knockouts which has no moving parts, can be fabricated in one or only a few simple metal working operations and is very inexpensive.

A significant feature of the present invention resides in the provision of means for removing the disc knockout from the center of the concentric ring knockout prior to removal of the latter.

These and other objects and advantages of the present invention will be more readily apparent from an understanding of the following detailed description of one embodiment of the invention where considered in conjunction with the accompanying drawings in which:

FIG. 1 is a side view of the tool of the present invention;

FIG. 2 is a fragmentary side view of the tool in one position of operation and a fragmentary sectional view of the electrical conduit box containing the disc and ring knockouts; and

FIGS. 3, 4 and are views similar to FIG. 2 showing the tool in successive positions of operation in removing a ring knockout.

DETAILED DESCRIPTION Referring now to the drawings and particularly to FIG. 4 thereof, there is shown a fragmentary portion of an electrical junction box 10 or the like in connection with which the tool of the present invention is intended to be used for the removal of concentric ring knockouts formed in the several walls of the box 10.

The general knockout construction 12 comprises a center circular disc 14 defined by a weakened or score line 16 formed in the wall 18 of the box, the weakened line 16 extending over almost a complete circle but being discontinued over a small are 20 to provide a short non-weakened connecting portion 21 for the disc 14 to the rest of the wall 18. A ring knockout 22 is formed by a concentric score or weakened line which extends in two almost semi-circular arcs 24 and 26. The arcs 24 and 26 are unjoined and terminate at one location 28 in order to provide a non-weakened connecting portion between the ring 22 and the rest of the wall 18; the arcs 24 and 26 are also unjoined at a diametrically opposite location 30 where adjacent ends of the arcs 24 and 26 are connected to the adjacent ends of the inner circle 16, thereby discontinuing the ring knockout 22 so that the latter does not interfere with the connection portion 21 between the center disc 14 and the rest of the box wall 18. By this construction both the disc 14 and the ring 22 are independently integrally connected to the wall 18 so that the disc 14 can be removed without in any way damaging or displacing the ring 22 if a small size aperture is desired.

It will be seem by reference to the portion of the wall 34 shown in cross-section in FIG. 4 that the disc and ring knockouts may be easily and preferably formed by punching the ring knockout slightly out of the plane of the wall 34 except at the connection locations 21 and .28, while maintaining the disc knockout 14 in the plane of the wall 34. The weakened lines defining the knockouts may be formed by other known metal working operations.

Referring now to the rest of the figures and particularly to FIG. 1, the illustrated embodiment of the tool,

, generally designated by the numeral 40, comprises an elongate body member 42 having a suitable handle portion 44 on which shall be designated as the rear end of the body member, the opposite end being the forward end as hereinafter more specifically described. The entire body member 42 may be conveniently formed from a single piece of relatively thin sheet metal stock and can be formed by one or relatively few simple stamping or punching operations performed on a suitable punch press.

The forward end of the body member is formed to provide a sheet member gripping structure designated generally by the numeral 46. The gripping structure an is formed as a one price unitary structure and, as indicated above, is integrally formed with the body member 42 at the forward end thereof. The sheet member gripping means comprises a pair of generally oppositely facing gripping grooves which, as best seen in FIG. 1, consists of a first generally forwardly facing groove 48 which is located adjacent but spaced from the forward end 50 of the body member 42 by a distance sufficient to provide an elongate bearing surface 52 extending from the groove 48 toward the front end 50. The functionof the bearing surface 52 will be made clear hereinafter. The groove 48 is actually defined by a rear portion of the bearing surface 52 and a short opposed surface 54 at the forward end of a substantially semicircular guide portion 56 of the gripping structure, the function of which will also be made clear hereinafter.

The gripping structure 46 also includes a second rearwardly facing groove 58 which is located at the rearward end of the guide portion 56 and is defined by a short surface 60 of the guide portion 56 and the forward end portion of a second bearing surface 62 which extends from the groove 58 rearwardly of the body member 42 for a distance at least as long as the first bearing surface 52.

The grooves 48 and 58 are spaced apart, as determined by the diameter of the guide portion 56, by a dis tanceslightly less than the interval diameter of the smallest ring knockout with which the tool is intended to be used so that the gripping structure 46 can be inserted into the aperture of the ring knockout in the manner hereinafter described. It will also be noted that the grooves 48 and 58 are disposed at a slight angle relative to each other in the plane of the tool to facilitate alternate engagement of opposite portions of the ring knockout 22 in the manner described below.

It will be seen that the bearing surfaces 52 and 62 are disposed at an angle relative to each other so that the ring knockout will be bent at an angle in the back and forth movement of the tool as described below. This helps to fracture the connecting points 28 and 30.

As a feature of the present invention, there is also incorporated into the gripping structure a means for conveniently removing the center disc knockout'14 which initially fills the aperture of the ring knockout. Thus, the aforementioned forward end 50 constitutes a blunt pointed nose which is adapted to be used as a striking means for initially displacing the disc knockout from its normal position. A longitudinal slot 64 is also provided adjacent the nose portion 50 by which the partially separated disc knockout can be grasped and twisted, thereby fracturing the disc knockout from the ring knockout.

in using the tool of the present invention, the follow ing procedure is exemplary of the utility of the tool of the present invention and the recommended manner of use. With reference to PKG. 2, initially the disc knock out M may be removed from the ring knockout 22 by placing the nose portion 50 of the tool against the disc knockout at a point opposite the connecting portion 21 and striking the opposite end of the tool with the hand or any suitable instrument. This pushes the disc knockout inwardly of the box, after which the slot is placed over the bent in disc knockout M and both tool and knockout are twisted back and forth in an oscillatory motion about the longitudinal axis of the tool until the connecting portion 21 fractures and the disc knockout-M falls away.

Thereafter, as specifically shown in FIG. 2, the guide portion 5a is inserted into the aperture of the ring knockout 22 and the forward groove 48 is engaged with a portion of the ring knockout 22-which is disposed away from the connecting portions 28 and 2% between the ring knockout 22 and the wall 18 of the box. When thus engaged, the handle 44 is moved downwardly or in a clockwise direction as viewed in FIG. 2 until the rear bearing surface 62 contacts the opposite outer surface portion of the ring knockout 22. it should be particularly noted at this point that the internal diameter of the ring knockout 22 is immaterial to the proper operation of the tool, this diameter being limited only to the length of the bearing surface 62 so as to provide a point of contact between the ring knockout 22 and the bearing surface 62 somewhere along the latter.

This point of contact, indicated by the numeral 66 in PKG. 3., now functions as a fulcrum about which the tool pivots in response to further downward or clockwise movement of the handle 44 with the result that the groove 48 forcibly raises the portion of the ring knockout 22 which is engaged therewith. This causes one half of the ring knockout to be bent out of the plane of the wall 118 about the connecting portions 22 and 3b as an axis to substantially the position. shown in H6. 3, thereby commencing the fracturing action of the connecting portions 28 and 3t).

Next, the tool is moved generally rearwardly with respect to the ring knockout 22 so that the tool moves from the position shown in FIG. 3 to that shown in lllG. d, that is, the forward groove 48 is disengaged from the forward portion of the ring knockout 22 and the rear ward groove 58 is engaged with the rear portion of the ring knockout 22. At this point, the tool is moved upwardly or in a counter-clockwise direction about the point of contact between the rear groove as and the rear portion of the ring knockout 22 as a pivot point until the forward bearing surface 52 contacts the wall 12 of the box, thus bending the forward portion of the ring knockout 22 substantially back into the plane of the wall 28. The reason for this is that the forward portion of the ring knockout 22 offers less resistance to bending movement than does the rear portion at this time. However, when the forward bearing surface $2 makes contact with the wall of the box, such as at the point indicated by the numeral 62 in FIG. 5, this point now becomes the pivot point about which further counterclockwise movement of the tool forces the rear por tion of the ring knockout to move upwardly and out of the plane of the wall 18 to the position shown in FIG. 5. At this point, both portions of the ring knockout 22 have been bent at least once about the connecting portions 28 and 30 as an axis and the fracturing of these portions has commenced.

in order to continue the fracturing action on the connecting portions 28 and 30, the tool is now moved generally forwardly to again engage the groove 48 with the forward portion of the ring knockout 22 as shown in FIG. 2 and the tool is moved in a clockwise direction. Since both forward and rear portions of the ring knockout have now been bent out of the wall 18 of the box at least once, the resistance to movement is about equal on both portions, as a result of which further oscillatory movement of the ring knockout takes place substantially about the axis defined by the connecting portions 28 and 30, with the ring knockout itself remaining bent at a constant angle. After the clockwise movement of the tool to the point where the rear bearing surface 62 stops the tool from further movement, the tool is again moved rearwardly to reengage the groove 58 with the rear portion of the ring knockout and is moved in a counter-clockwise direction until the forward bearing surface 52 stops further movement.

It will thus be seen that the combined forward and rearward movement of the tool alternately engages the forward and rear gripping grooves with the forward and rear portions respectively of the ring knockout, and this movement, combined with the oscillatory movement described above causes the ring knockout to be bent about the connecting portions 28 and 30 until the latter fracture from the wall 18 thereby permitting the knockout to fall free. In practice, it generally requires about 4 to 8 oscillatory movements of the tool to fracture the knockout, depending on the thickness of the wall 18.

, The circular guide portion 56 functions to prevent the tool from accidentally abutting the underside of the sheet metal member and consequently not permitting a proper rocking motion. Thus, in some cases where the ring knockout is much narrower than the depth of the grooves, and if one side of the ring knockout fractures before the other side, the outer lip of the grooves may inadvertently catch on the outer edge of the sheet member 18 and prevent proper operation of the too] if the grooves are formed merely by a flat edge extending from one groove to the other. The guide portion 56 assures that a portion of the gripping structure remains within the opening in the sheet member 18 at all times until the ring knockout is completely fractured so that theabove malfunction cannot occur. The guide portion will merely ride along the edge of the opening under the conditions mentioned above and maintain proper operation of the tool.

I claim:

1. A tool for removing concentric ring knockouts from a relatively thin sheet member, said knockouts being defined by concentric weakened lines on said sheet member, said ring knockouts having a predetermined variable internal diameter and having portions integrally connecting the knockouts with said sheet member, said tool comprising:

A. an elongate body member having a handle portion at a rearward end of said body member,

B. a one piece unitary sheet member gripping structure integrally formed with said body member at the forward end thereof, said gripping structure comprising 1. opposed gripping means spaced apart a predetermined distance less than the predetermined internal diameter of said ring knockouts whereby said gripping means is insertable into the aperture defined by said ring knockouts and is movable therein forwardly and rearwardly to alternately engage opposite surfaces of diametrically opposite portions of said ring knockouts with said gripping means, and

2. bearing surfaces disposed on said gripping structure forwardly and rearwardly of said gripping means, said bearing surfaces extending for a distance greater than said predetermined spaced apart distance of said gripping means thereby limiting the extent to which said gripping means is insertable into said aperture and defining pivot points adjacent said gripping means engageable with said sheet member about which said tool is successively rocked in a clockwise and counterclockwise direction when said gripping means is engaged respectively with a forward and rearward portion of a ring knockout whereby the ring knockout is rocked about the connections thereof with the sheet member to fracture the connecting portions from the sheet member.

2. A tool according to claim 1 wherein said gripping means comprises a pair of diametrically opposed forwardly and rearwardly facing grooves formed in said body member adjacent the forward end thereof, the forwardly facing groove being spaced from the forward end of said body member a distance sufficient to provide an elongate surface between said forward end and said forwardly facing groove, said surface defining one of said bearing surfaces.

3. A tool according to claim 2 wherein the other of said bearing surfaces is defined by a surface of the body member extending rearwardly from the rearwardly facing groove of said pair of grooves.

4. A tool according to claim 3 wherein said bearing surfaces are disposed at an angle relative to each other to facilitate bending of the concentric ring knockout as the latter is rocked back and forth about the connecting portions thereof with the sheet member. I

5. A tool according to claim 1 wherein said gripping structure includes guide means formed integrally with said gripping structure and located intermediate said opposed gripping means for preventing said gripping means from engaging and part-of the thin sheet member other than the concentric ring knockout.

6. A tool according to claim 5 wherein said guide means comprises a substantially semi-cylindrical portion of said body member extending between said opposed gripping means and extending inwardly toward the aperture defined by the ring knockout.

7. A tool according to claim 1 wherein said body member includes a blunt pointed nose portion at the forward end of the body member, and a longitudinal slot formed in said body member adjacent said nose portion whereby the central disc portion of the ring knockout is partially fractured by being struck with the nose portion of the tool and completely fractured by being twisted after engagement of the disc with said longitudinal slot.

. it i 

1. A tool for removing concentric ring knockouts from a relatively thin sheet member, said knockouts being defined by concentric weakened lines on said sheet member, said ring knockouts having a predetermined variable internal diameter and having portions integrally connecting the knockouts with said sheet member, said tool comprising: A. an elongate body member having a handle portion at a rearward end of said body member, B. a one piece unitary sheet member gripping structure integrally formed with said body member at the forward end thereof, said gripping structure comprising
 1. opposed gripping means spaced apart a predetermined distance less than the predetermined internal diameter of said ring knockouts whereby said gripping means is insertable into the aperture defined by said ring knockouts and is movable therein forwardly and rearwardly to alternately engage opposite surfaces of diametrically opposite portions of said ring knockouts with said gripping means, and
 2. bearing surfaces disposed on said gripping structure forwardly and rearwardly of said gripping means, said bearing surfaces extending for a distance greater than said predetermined spaced apart distance of said gripping means thereby limiting the extent to which said gripping means is insertable into said aperture and defining pivot points adjacent said gripping means engageable with said sheet member about which said tool is successively rocked in a clockwise and counter-clockwise direction when said gripping means is engaged respectively with a forward and rearward portion of a ring knockout whereby the ring knockout is rocked about the connections thereof with the sheet member to fracture the connecting portions from the sheet member.
 2. bearing surfaces disposed on said gripping structure forwardly and rearwardly of said gripping means, said bearing surfaces extending for a distance greater than said predetermined spaced apart distance of said gripping means thereby limiting the extent to which said gripping means is insertable into said aperture and defining pivot points adjacent said gripping means engageable with said sheet member about which said tool is successively rocked in a clockwise and counter-clockwise direction when said gripping means is engaged respectively with a forward and rearward portion of a ring knockout whereby the ring knockout is rocked about the connections thereof with the sheet member to fracture the connecting portions from the sheet member.
 2. A tool according to claim 1 wherein said gripping means comprises a pair of diametrically opposed forwardly and rearwardly facing grooves formed in said body member adjacent the forward end thereof, the forwardly facing groove being spaced from the forward end of said body member a distance sufficient to provide an elongate surface between said forward end and said forwardly facing groove, said surface defining one of said bearing surfaces.
 3. A tool according to claim 2 wherein the other of said bearing surfaces is defined by a surface of the body member extending rearwardly from the rearwardly facing groove of said pair of grooves.
 4. A tool according to claim 3 wherein said bearing surfaces are disposed at an angle relative to each other to facilitate bending of the concentric ring knockout as the latter is rocked back and forth about the connecting portions thereof with the sheet member.
 5. A tool according to claim 1 wherein said gripping structure includes guide means formed integrally with said gripping structure and located intermediate said opposed gripping means for preventing said gripping means from engaging and part of the thin sheet member other than the concentric ring knockout.
 6. A tool according to claim 5 wherein said guide means comprises a substantially semi-cylindrical portion of said body member extending between said opposed gripping means and extending inwardly toward the aperture defined by the ring knockout.
 7. A tool according to claim 1 wherein said body member includes a blunt pointed nose pOrtion at the forward end of the body member, and a longitudinal slot formed in said body member adjacent said nose portion whereby the central disc portion of the ring knockout is partially fractured by being struck with the nose portion of the tool and completely fractured by being twisted after engagement of the disc with said longitudinal slot. 